1. Field of the Invention
The present invention relates to hearing aids and to methods of fitting hearing aids. This invention more specifically relates to the fitting of hearing aid systems to individual users, in particular to the fitting of systems utilizing some form of digital signal processing in the fitting chain.
2. The Prior Art
Talk-over or talk-back systems are used in a wide variety of applications, for instance in professional recording or broadcasting studios in the music industry, where they enable an auditive communications link from the control room to the studio itself. In these settings, the talk-back function enables the audio engineer or the producer to provide anyone in the studio with information, instructions or requests. The talk-back function is usually activated by a dedicated switch, conveniently placed on the mixing console or elsewhere in the control room, and relies on a talk-back microphone placed in the control room, a dedicated signal pathway and means for reproducing the signal from the talk-back microphone to the person(s) in the studio. To the best knowledge of the inventor it has, however, never been applied to the field of hearing aid fitting, perhaps due to the practical limitations involved.
U.S. Pat. No. 2,255,517 discloses a talk-back communication system permitting a plurality of remote transducer terminals to make replies to voice communication from a central transducer terminal. The talk-back signal path is initiated by activating a push button switch at any one of the remote transducer terminals, thereby temporarily breaking the normal signal path from the central transducer terminal to the remote transducer terminal in question, and restoring the normal signal path again by release of the switch when communication from the remote terminal ceases. This system, however, does not deal with transmission through a narrow-band communication channel, nor does it incorporate any digital signal path.
U.S. Pat. No. 6,360,093 B1 discloses a system for wireless voice broadcasting utilizing a computer network for delivering telephony between a number of wireless terminals via an internet or intranet server in a coded, digital audio format. Any of the wireless terminals may initiate transmission at any time, as the server software controls the signals from the individual transmitters.
WO 01/56331 provides an auditory prosthesis together with a programming device and means for transmitting signals from the hearing aid to the programming device.
EP 0453450 A1 discloses a device for wirelessly communicating programming data from a personal computer to a receiving hearing aid. During programming, the PC, running suitable hearing aid programming software, communicates instructions regarding gain in different frequency bands, compression, etc. to the hearing aid.
DE 19541648 describes a setup with a PC equipped with a transmitter/receiver module in wireless communication with a mobile transmitter module connected to a hearing aid.
Commercial systems for wireless programming of hearing aids via a link device are optimized for high throughput and simple hardware. This is achieved by using a variable bit rate and a relatively large digital packet size in the buffered communication protocol used. In a setup of this kind, the attainable bandwidth is about 250 kbps, which is sufficient for programming but unusable for uncompressed audio with full frequency range, claiming a bandwidth of around 2 Mbps.
Within the field of telecommunications it is known to reduce the bandwidth of an audio signal prior to digital conversion and transmission, for instance to a bandwidth of 64 kbps fixed rate transmission, as used in a standard ISDN telephone connection. However, driving a 64 kbps fixed rate transmission through a link device utilizing a variable bit-rate protocol requires a high rate of data packet transmissions, and thus, the number of data packets required for providing an effectively continuous transmission would be so large that the overhead in buffering and processing the individual data packets in the link device would consume too much time for the link device processor to achieve a continuous transmission without loss of some of the packets due to buffer overflow.
Recent development in digital hearing aids has provided fitters and audiologists with advanced tools for determining hearing loss, for selecting and fitting suitable hearing aids to compensate for the hearing loss, and for fine tuning hearing aids to match the user's hearing loss profile as closely as possible. The digital technology permits the use of dedicated software for performing these tasks by programming appropriate parameter values into the hearing aid processor. The most advanced, programmable hearing aids provide for several programmes to be stored in the memory of a hearing aid for instant recall and use at any one time by the hearing aid user.
Fitting of modem hearing aids to an individual user is typically performed by the audiologist by using the values from an individual audiogram determined at an earlier stage. The audiogram data are processed according to a fitting rule in order to determine suitable settings for optimum compensation of the user's hearing deficiency. The parameter settings are subsequently programmed into a hearing aid.
The fit may be tested and fine tuned in a procedure where the user is placed in a selected acoustic environment and allowed to listen and to test variations in the settings. For testing, simulated acoustic environments are generated in a test chamber, where the user is located. The audiologist will conduct the testing and will remotely adapt the hearing aid settings.
The fitting is an interactive procedure between the audiologist and the user. During the fitting, however, communication from the audiologist to the hearing aid user can be a real problem. A dedicated talk-over system could be used for this purpose, however, this represents an added capital cost and complication.